1. Field of the Invention
This invention relates to a method for reducing off-taste and/or odor from hygienic paper packages (such as food and beverage packaging). Such methods of this type, generally, remove undesirable compounds that create off-taste and/or odor from the paper package in a simple, cost-effective manner.
2. Description of Related Art
Packaging materials can impart a taste and/or odor to items contained inside. This is particularly a problem if the package is used for food products. The strong odor from the package can be absorbed by the food, thereby, making the food unpalatable.
The sources of the off-taste/odor are either the materials in printing the package (solvents, inks, etc.) or compounds of the package (paper, plastic coating, etc.). In many situations, printing materials are the predominate source of taste and/or odor in the package.
While there has been considerable work done in minimizing tastes/odors from the printing process, there has been minimal work on decreasing the taste from unprinted paper materials.
Taste and odor are subjective qualities. What may be objectionable to one person can be acceptable to another. This subjectiveness makes identifying the source of an off-taste/odor difficult. To further complicate identifying the source of the problem, taste and odor are rarely the result of a single chemical compound. Typically, it is a combination and/or interaction of multiple chemicals that results in a certain taste. For example, hundreds of compounds have been detected in coffee and are responsible for its characteristic taste and odor. To limit the subjectivity, odor and taste panels are used to evaluate a product.
While certain inorganic materials have a strong taste or odor (ammonia or hydrogen sulfide) most odors are due to organic compounds. Of the organic compounds, humans have more taste/odor sensitivity towards oxygenated compounds. For example, the average odor threshold for n-butane is 1000 ppm while for butyric acid it is 0.0001 ppm. This is also the reason most perfumes are esters. This is also the reason ketones give distilled spirits their characteristic taste. Another characteristic of odor causing compounds is their volatility.
As mentioned earlier, many off-taste/odor problems are due to solvents and materials used in the printing operations. However, there are several compounds in unprinted paper packaging that will affect the taste such as Octenol, Hexanal, Butyric acid, etc. These compounds are likely inherent to the papermaking process and are probably the result of the chemical reactions that occur in the pulping and/or bleaching process.
Prudence dictates that the best way to minimize off-taste/odor is to prevent it from occurring. For example, in the papermaking process, volatile fatty acids are apparently formed by microbiological fermentation. The fermentation occurs mainly in the holding tanks and the papermachine forming section ("wet end"). Fermentation can be minimized by adding biocides or slimicides at specific points in the pulp and papermaking process. By eliminating/minimizing the microbiological contamination present, the fatty acids are precluded from forming.
Similarly with the printing process, it is preferable to prevent them from occurring instead of treating them. For example, one can use low odor inks and varnishes in the printing process thereby avoiding some of the problems in the printing area. Similarly, one can use a solvent that does not contain high boiling residues ("tails") which can cause an odor.
Another solution used in the printing industry is to operate the printing process so that the solvent retained in the paper is low. Low solvent retention is achieved by increasing the temperature and/or time in the drying hoods. Exemplary of such prior art is U.S. Pat. No. 4,818,342 ('342) to D. G. Wagle et al., entitled "Heat Treatment of Paper Products". While the '342 patent describes a method for which the paper is dried to an extremely low moisture content then rewet, care must be exercised because if the paper is "over dried", the physical properties of the paper deteriorate and the print quality decreases. This "over drying" causes embrittlement of the paper and affects the ink's absorption properties.
Plastic and extruded paperboard also can be a source of off-taste/odors. For example, it is well recognized in the industry that extruding at higher temperatures increases the likelihood of forming an off-taste. In this instance, the problem is corrected by lowering the extruder die temperature.
Previous work suitable for use with unprinted packaging focused on absorption to reduce the concentration of compounds that generate off-taste and/or odor. The absorption is accomplished by adding aluminum silicate to the pulp going to the wet end of the paper machine. Typical addition rates are 0.5-2 kg/ton. While this may be a solution to the off-taste/odor problem it has several drawbacks. One drawback is that the effectiveness is dependent on the retention of the aluminum silicate in the paper fiber. If there is naturally poor retention, then additional chemicals must be used to promote adhesion of the aluminum silicate onto the paper fibers. Also, this does not eliminate the compounds causing taste and odor problems, it merely adsorbs them.
It is apparent from the above that there exists a need in the art for a method which reduces off-taste and/or odor from a paper package, and which at least equals the off-taste/odor removal characteristics of the known techniques, but which at the same time substantially removes the off-taste and/odor in a simple, cost-effective manner. It is the purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.